Pests, plant diseases, and weeds can be serious threats to crops. Losses due to pests and diseases have been estimated at 37% of the agricultural production worldwide, with 13% due to insects, bacteria and other organisms.
Toxins are virulence determinants that play an important role in microbial pathogenicity and/or evasion of the host immune response. Toxins from the gram-positive bacterium Bacillus, particularly Bacillus thuringiensis, have been used as insecticidal proteins. Current strategies use the genes expressing these toxins to produce transgenic crops. Transgenic crops expressing insecticidal protein toxins are used to combat crop damage from insects.
While the use of Bacillus toxins has been successful in controlling insects, resistance to Bt toxins has developed in some target pests in many parts of the world where such toxins have been used intensively. One way of solving this problem is sowing Bt crops with alternating rows of regular non Bt crops (refuge). An alternative method to avoid or slow down development of insect resistance is stacking insecticidal genes with different modes of action against insects in transgenic plants. The current strategy of using transgenic crops expressing insecticidal protein toxins is placing increasing emphasis on the discovery of novel toxins, beyond those already derived from the bacterium Bacillus thuringiensis. These toxins may prove useful as alternatives to those derived from B. thuringiensis for deployment in insect- and pest-resistant transgenic plants. Thus, new toxin proteins are needed.